buffer problem?

Question

A buffer solution contains 0.16 mol of acetic acid and 0.13 mol of sodium acetate in 1.15 L.
What is the pH of this buffer?
What is the pH of the buffer after the addition of 0.05 mol of KOH?
What is the pH of the buffer after the addition of 0.01 mol of HNO3?

Answer 1

0.16 mol in 1.15 l---therefore 0.14mol in 1.0 l.similarly 0.11 mol in 1l

pH=Pk+log [Salt]/[Acid]

pH=5.0+log 0.11/14----log 0.11-log 0.14

Calculate..verify pK of Acetic acid is 6.1 or 5.0